1. Field of the Invention
The present invention relates to photovoltaic battery rechargers and particularly to a portable photovoltaic battery recharger for simultaneously recharging a plurality of batteries having different sizes and respective optimum charging current levels.
2. Description of the Related Art
Numerous photovoltaic battery recharging kits are known in the art which provide the capability of recharging batteries through the direct conversion of sunlight into electrical current. An example of such prior art solar energy rechargers is shown in U.S. Pat. No. 4,209,346 which describes a portable power supply for a rechargeable battery which includes an array of solar cells and a heat sink thermally engaging the cells and the batteries for transmission of power from the cells to the batteries.
However, these prior art attempts at providing a portable photovoltaic power source for recharging batteries are limited in that each is configured with a single array of commonly sized solar cells. The commonly sized solar cells of the array produce only a single charging current level since the charging current level is directly proportional to the surface area of the individual cells. Some of the prior art photovoltaic battery rechargers incorporate elaborate electrical circuitry for switching between selected ones of the commonly sized solar cells. However, such elaborate circuitry requires corresponding increases in cost and complexity of manufacture of the device.
Normally, each respective photovoltaic solar cell of the array of cells of the prior art rechargers is selected to provide a charging current level matched to whatever size battery is intended for use with the recharger. Thus, if any other size battery, other than the base line design battery, is connected to the portable power source, that battery is not recharged at the optimum recharging current level. Rather, either a higher or lower recharging current level, depending on the base line design, is provided to the battery, and may result in either degradation of the life of the rechargeable battery in the event the charging current level is higher than the optimum value, or an unnecessarily high recharging time to replenish the battery if the charging current level is less than the optimum value.
It is thus an object of the present invention to provide a portable photovoltaic battery recharger which simultaneously recharges a plurality of rechargeable batteries having different sizes and capacities at each battery's respective optimum charging current level.
It is a further object of the present invention to provide a photovoltaic battery recharger for simultaneously recharging a plurality of batteries of different sizes which is lightweight, portable, and simple in construction.
It is still a further object of the present invention to provide a photovoltaic battery recharger for simultaneously recharging a plurality of batteries of different sizes wherein the circuit means which connects the photovoltaic cells to the batteries is simple in construction, inexpensive to manufacture, and includes a means for preventing discharge of the batteries through the solar cells when the cells are not insolated.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.